1. Field of the Invention
The present invention relates to an image display system which converts image data into display data using display parameters set by an operator and displays image information. More particularly, this invention relates to an image display system which is for use in a system involving plural types of display parameters contributing to emphasis of image information components and can effectively set display parameters.
2. Description of the Related Art
In displaying a CT (Computerized Tomography) image on a display of a CT apparatus, since image information of a CT image has a significant number of gradations compared with the display performance of the display, the desired gradation characteristic is given to a desired part of the entire gradation range for image display. Such processing is performed on not only a CT image but also other various types of image information. With regard to medical diagnosis images, for instance, similar processing is performed on image information, such as an MR (Magnetic Resonance) image, digital radiographic image and nuclear medicine image. In such a case, normally, original image data is converted into display data affixed with display gradation normally varying on a linear base within a gradation level range of a desired window width (WW), i.e., a desired level width around a desired level or window level (WL) of the whole gradation level. The window level (WL) and window width (WW) are conversion parameters used in converting image data into display data. The conversion parameters are called display parameters. In many systems, the window width (WW) and window level (WL) are altered by an operator's operating a switch or a key on a keyboard or rotating a knob, and an image corresponding to the window width (WW) or window level (WL) at that time is sequentially displayed. The operator repeats the above operation to change the window width (WW) and window level (WL) as desired, thereby acquiring the desired, corresponding display images.
The relation between the values of the window width (WW) and window level (WL) and a desired or required display image is not always clear or known to the operator. The operator, therefore, should properly set and vary the window width (WW) and window level (WL) to understand how the display image changes with a variation in these values to thereby cause the resultant display image to gradually approach the desired one. This inevitably requires great amounts of time and labor for the adjustment. Depending on the initial values of the window width (WW) and window level (WL) selected in the adjustment, however, part of that information included in the image data which is beneficial or interesting to the operator may not appear in the display image, so that the operator is likely to overlook it.